I have two SS Brewtech conical fermenters with the FTSS heating and cooling systems which also have the neopreme insulation covers. I have had them for over 6 years. I hose them off with the covers on during cleaning and have never had any issue. I recently bought the shelves that allow you to put the temperature controllers just above the thermowell (rather than on top of the lid)(see FTSs Controller Mounting Bracket - Threaded for SS Brewmaster Edition Chronicals & Standard Brite Tanks - FT-CNTRBKT-001 ) and had to remove the covers to install them. When I took the neopreme covers off, everything underneath was nice and clean and shiny. No issues.